The present invention relates generally to a projection screen and a projection type display system, and more particularly to a projection type display system that enables a single image projected onto a projection screen to be viewed from at least two different directions at the same time, and a projections screen used with the same.
So far, it is general that to allow an image projected from a single projector to be simultaneously viewed from a plurality of different directions, projection light is diffused through a projection screen having a large angle of diffusion in a wide range, in which different viewers or both eyes are positioned to view a projected image.
Patent Publication 1
JP-A 2003-177221
Patent Publication 2
JP-A 9-127312
Patent Publication 3
JP-A 2000-171618
However, the use of a projection screen having a large angle of diffusion causes projection light from a single projector to be diffused over a wide range, and to enable bright images to be viewed at individual positions, a strong illumination light source must be used, resulting unavoidably in an increase in the size of the projector and increased power consumption.
In view of such problems with the prior art, a primary object of the present invention is to provide a projection screen and a projection type display system adapted to diffuse projection light from a single projector intensively into at least two viewing areas each having a relatively narrow extent, so that two or more viewers can view the same image at the same time.
According to the present invention, this object is achievable by the provision of a projection screen, characterized in that a plurality of Fresnel concave mirrors are superposed on the same substrate in a mutually decentered fashion.
Preferably in this case, a diffusing plate is located on a side of the projection screen on which projection light is to be incident or a side of the projection screen at which projection light is to be reflected.
For the diffusing plate, it is desired to use a diffusing plate comprising a transmission hologram.
The present invention also includes a projection type display system comprising an image display device, a projection optical system for magnifying and projecting an image displayed on said image display device and a projection screen located in the vicinity of an image projected through said projection optical system, characterized in that said projection screen comprises any one of those as recited above.
With the projection screen of the invention wherein a plurality of Fresnel concave mirrors are superposed on the same substrate in a mutually decentered fashion, projection light projected from a single projector can be intensively directed to at least two viewing areas each having a relatively narrow extent, so that the same image can be viewed at the same time by both eyes or two or more viewers.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.